Utilization of adsorptive bubble chromatography for oleuropein enrichment from olive leaves: Parameter optimization based on mathematical modeling

The natural and economical extraction of bioactive compounds required for industrial-scale production, along with the integration of waste materials into the process, has become a critical focus in both academic and industrial research. In this context, the enrichment of oleuropein in olive leaf extract was targeted using the Adsorptive Bubble Chromatography (ABC) method. Prior to the ABC process, different extraction techniques, including Reflux Extraction (CE), Microwave-Assisted Extraction (MAE), and Maceration (Mc), were applied with various operational parameters to obtain high-quality olive leaf extract (OLE). The most suitable extraction method was determined through a two-fold optimization approach. The first optimization focused on antioxidant activity, total phenolic content, and total flavonoid content, while the second targeted the bioactive compound composition of oleuropein. A comprehensive optimization study using Response Surface Methodology (RSM), SPSS, and Principal Component Analysis (PCA) determined that the CE method with a 90-minute extraction time was the most effective extraction technique. During the ABC process, soy lecithin was used as the surfactant, and critical parameters such as surfactant concentration, feed sample pH, gas flow rate, column length, and enrichment duration were optimized. The enrichment ratios of various bioactive compounds, including oleuropein (Olp), hydroxycinnamic acid (Hc-Ac), quersetin (Qrc), luteolin (Ltl), caffeic acid (Cf-Ac), hydroxybenzoic acid (Hyb), alizarin (Alz), curmin (Crm), ellagic acid (El-Ac), protocatechuic acid (Pr-Ac), thymoquinone (Thq), resveratrol (Rsv), phloridzindihydrate (Phl), and syringic scid (Sy-Ac), were analyzed. Additionally, mathematical models were developed to evaluate the Extract Enrichment Ratio and Extract Recovery Percentage, with the statistical effects of different operational parameters examined in detail. As a result of the optimization study for oleuropein enrichment using the ABC method, the highest enrichment ratio of oleuropein was determined to be 12.66%. The optimal operating conditions were identified as 14.28 g/L surfactant concentration, pH 5, 1.5 mL/s gas flow rate, 50 cm column length, and a 15-minute enrichment time, with a compliance coefficient of 0.859 confirming the validity of the findings. These results demonstrate that the ABC method is an effective and feasible technique for the purification of oleuropein and phenolic compounds. This study serves as a significant scientific reference for the pharmaceutical, food, and cosmetic industries.